Having multiple children

How do you do it? I have one toddler and I get so overwhelmed and stressed easily. We just started trying for number 2 and I get so worried sometimes that I won’t mentally be able to handle it. Genuinely how do you handle more than one kid? Mentally is my biggest worry because I am bipolar but I’m medicated for it. Lately my toddler has been sleeping badly and I wonder how I could handle her sleeping bad and having a newborn if she still is at that time. I really do want a second baby but it’s so hard to feel like I can do it